Exams > Cat > Quantitaitve Aptitude
BASIC ALGEBRA MCQs
:
A
Let the three consecutive terms be ar,a,ar
Product = (ar)(a)(ar) = a3 = 512, ⇒ a = 8
Sum of these numbers =a(1+r+1r)=42⇒8(1+r+1r)=42
4r2−17r+4=0
(4r – 1)(r – 4) = 0
r = 14or r = 4.
Hence the largest number is 32. The series is 32, 8, 2 or 2, 8, 32.
:
A
The first two terms = a, ar
a+ar= 53
a(1−r)=3
a=3(1−r)
a(1+r)=53
3(1−r)(1+r)=53
1−r2=59
r2=49
r=23
a=3(1−23)=1
First term is 1.
:
C
Let the numbers be x and y.
x+y=30
xy = 144
(x−y)2=(x+y)2−4xy
900−(4×144)=324
hence (x–y)=18
Solving:x−y=18 & x+y=30
x = 24, y = 6
So, the bigger number is 24.
:
A
G.M=(A.M×H.M)12
64=10×H.M
H.M=6.4
:
B
6x2−4x+3x−2=0
2x(3x−2)+1(3x−2)=0
(2x+1)(3x−2)=0
The roots are:−12,23
:
A
Soln:
The 3rd term will be x+2d
The 15th term will bex+14d
From the information given in the question,
x+2d+x+14d=x+5d+x+10d+x+12d
Solving we get,x+11d=0, this is nothing but the 12th term of the series.
:
B
Let x3=y
y2−26y−27=0
y2−27y+y−27=0
y(y−27)+1(y−27)=0
(y+1)(y−27)=0
The roots are y = -1, y = 27
x3=−1,x=−1
x3=27,x=3
:
B
[(x+1)(x+4)][(x+2)(x+3)]=24
(x2+5x+4)(x2+5x+6)=24
Let x2+5x=k
(k+4)(k+6)=24
k2+10k=0
k(k+10)=0
k=0,k=−10
x2+5x=0,x2+5x=−10
x(x+5)=0,x2+5x+10=0
x=0,x=−5;D=25−40=−15 No real roots.
So, roots are 0, -5.
:
A
Let x−1x=z
(x−1x)2=z2
(x2+1x2−2)=z2
x2+1x2=z2+2
Now substituting in the equation:
6(z2+2)−25z+12=0
6z2+12−25z+12=0
6z2−25z+24=0
6z2−16z−9z+24=0
2z(3z−8)−3(3z−8)=0
(2z−3)(3z−8)=0
z=32 ; z=83
x−1x=32
x−1x=83
2x2=3x−2=0
3x2−8x−3=0
2x2−4x+x−2=0
3x2−9x+x−3=0
2x(x−2)+1(x−2)=0
3x(x−3)+1(x−3)=0
(2x+1)(x−2)=0
(3x+1)(x−3)=0
x=−12 , x=2
x=−13 , x=3
So,the roots are:−12,2,−13,3
:
C
2x.23+2−x=6
Let 2x=z
8z+1z=6
8z2+1=6z
8z2−6z+1=0
8z2−4z−2z+1=0
4z(2z−1)−1(2z−1)=0
(4z−1)(2z−1)=0
z=14,
z=12
2x=14
x=−2
2x=12
x=−1
Roots are x=−2,x=−1